Alice, an anonymous informant, would like to transmit digital documents to Bob while maintaining her anonymity.
For whatever reason, she chooses to copy the documents to some kind of physical removable storage, for example: USB flash drives, external hard drives or DVD-ROM / BD-ROM, and deliver the media to Bob via sneakernet.
(Assume it's possible to deliver the physical media to Bob anonymously, there's no physical identifiable evidence (fingerprints, etc.), and the documents themselves do not contain identifiable information.)
In what ways may Alice inadvertently leave identifiable information in the removable storage, so that Bob can trace back to Alice?
I am looking for answers that apply uniquely to the usage of physical media, as opposed to e.g. transferring the documents by Internet. For an obvious example: If Alice edited a
.docx file with Microsoft Word, she may have left identifiable metadata in the file. However such metadata will be available whether she used sneakernet or Internet to transfer that document, so this is not a valid answer for this question.
Some ideas I can think of:
- DVD / Bluray burners writing their serial numbers to the blank media. (We know laser printers encode their serial numbers in printouts. Do optical drives do something similar?)
- Identifiable metadata in file system, either at FS creation or with files stored in them. For example, I imagine NTFS knows a user's SID if any file has permissions assigned for that user. Does e.g. casually copying a file from "My Documents" to an NTFS-formatted flash drive leave your SID in that flash drive? What about Linux file systems? A bare UID:GID doesn't seem very identifiable, but what about ACL?
- Serial number of the media itself. Perhaps the serial number of a portable hard drive can somehow be traced back to the purchaser.
How plausible are any of these scenarios above? What else can you think of?